This is an adapter to connect a 120mm computer fan to a typical 3" flexible duct. The are lots of good uses such as:

• Workshop venting
• Soldering station venting
• Solar kiln circulation (for drying wood)
• Boat ventilation (pull air from the bilge or from deep inside and vent it outside to prevent mildew/mold)

I built this to use direct with a solar panel to feed the 12v 120mm fan, but your fan needs may differ. Here are a few I can recommend with different specs:

• https://www.amazon.com/gp/product/B000O8I474/ref=as_li_qf_asin_il_tl?ie=UTF8&tag=digitalarseal-20&creative=9325&linkCode=as2&creativeASIN=B000O8I474&linkId=990609196467bdbe71826e1e2c5a9cd8 - 44CFM @ 23dB - This is a 4-pack of fans for a great low price, fairly quiet, but doesn't move a ton of air.
• https://www.amazon.com/gp/product/B000O8I474/ref=as_li_qf_asin_il_tl?ie=UTF8&tag=digitalarseal-20&creative=9325&linkCode=as2&creativeASIN=B000O8I474&linkId=990609196467bdbe71826e1e2c5a9cd8 - This fan can move up to 300CFM, but is a but louder. It was tested to move 300CFM at 16.2v 3A, 200CFM at 12v 2A, and 140CFM at 8v 1A

You'll also need either 4 bolts to connect the fan to the adapter or you can also use 4 zip ties. A larger zip tie or hose clamp is needed to connect the hose to the adapter. Here are some recommendations for the hose, hose clamps, and zip ties:

• https://www.amazon.com/gp/product/B000O8I474/ref=as_li_qf_asin_il_tl?ie=UTF8&tag=digitalarseal-20&creative=9325&linkCode=as2&creativeASIN=B000O8I474&linkId=990609196467bdbe71826e1e2c5a9cd8 - 3in x 50ft vinyl duct with a wire reinforcement.
• https://www.amazon.com/gp/product/B000O8I474/ref=as_li_qf_asin_il_tl?ie=UTF8&tag=digitalarseal-20&creative=9325&linkCode=as2&creativeASIN=B000O8I474&linkId=990609196467bdbe71826e1e2c5a9cd8 - 4-pack of 3" 304 Stainless Steel hose clamps.
• https://www.amazon.com/gp/product/B000O8I474/ref=as_li_qf_asin_il_tl?ie=UTF8&tag=digitalarseal-20&creative=9325&linkCode=as2&creativeASIN=B000O8I474&linkId=990609196467bdbe71826e1e2c5a9cd8 - 100-pack 12" zip ties - These are 3.5mm wide, and will fit through the bolt holes to attach the fan to the adapter, and can also be used to hold the 3" duct to the adapter. These are plenty strong for the 44CFM fans, but you might want to use the metal hose clamps instead if you are running a higher CFM fan.